At least 19 people remain missing after a huge blast at an explosives factory in the US state of Tennessee, a local official said, with the incident causing an unspecified number of "fatalities."

"At this time we have been able to confirm that we do have 19 souls that we're looking for," said Humphreys County Sheriff Chris Davis at a press conference on Friday.

"I can tell you that we've had, there are fatalities. I don't want to put a number to that... I can tell you right now we are looking for 19 individuals."

Aerial footage broadcast by US media showed smoldering debris at the blast site in Hickman County, with charred and mangled vehicles strewn across the facility.

Davis said authorities had secured the area, but warned of the possibility of smaller explosions around the site.

Accurate Energetic Systems, an explosives manufacturer founded in 1980, did not immediately respond to AFP's request for comment.

The company's Facebook page says it manufactures "various high explosive compositions and specialty products" for the US Department of Defense, now rebranded as the Department of War, as well as US industrial markets.